WO2005106060A1 - Fil ou barre d’acier présentant une haute résistance et une excellente usinabilité au froid, ou article modelé a haute résistance et processus de fabrication de ceux-ci - Google Patents

Fil ou barre d’acier présentant une haute résistance et une excellente usinabilité au froid, ou article modelé a haute résistance et processus de fabrication de ceux-ci Download PDF

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Publication number
WO2005106060A1
WO2005106060A1 PCT/JP2005/007352 JP2005007352W WO2005106060A1 WO 2005106060 A1 WO2005106060 A1 WO 2005106060A1 JP 2005007352 W JP2005007352 W JP 2005007352W WO 2005106060 A1 WO2005106060 A1 WO 2005106060A1
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Prior art keywords
strength
steel wire
cold
steel
less
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PCT/JP2005/007352
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English (en)
Japanese (ja)
Inventor
Shiro Torizuka
Eijiro Muramatsu
Kotobu Nagai
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National Institute For Materials Science
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Application filed by National Institute For Materials Science filed Critical National Institute For Materials Science
Priority to US11/547,972 priority Critical patent/US20080041503A1/en
Priority to CN2005800146445A priority patent/CN1954088B/zh
Publication of WO2005106060A1 publication Critical patent/WO2005106060A1/fr
Priority to US12/556,420 priority patent/US20100051144A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0093—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for screws; for bolts
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the invention of this application relates to a high-strength molded product such as a high-strength steel wire or a steel rod excellent in cold workability or a screw or a port using these characteristics, and a high-strength molded product of such a steel wire or a bar steel. Bright regarding manufacturing method. Background art
  • screws, bolts, and other high-strength parts for mechanical structures manufactured by forming steel wires or steel bars by cold working such as cold heading, rolling and Z or cutting, are manufactured by hot working.
  • the obtained steel wire rod is processed into a steel wire having a desired wire diameter by cold working, and the obtained steel wire is heated at a temperature of about 700 ° C. for a long time of about ten to several hours to about one day and night.
  • a so-called spheroidizing annealing treatment to soften the material and improve cold workability such as cold heading, it is formed into a product shape for various applications are doing.
  • the molded product processed in this way does not satisfy the required strength as the final product due to the softening treatment described above, so it is necessary to perform a tempering treatment such as quenching and tempering. I have.
  • Patent Document 1 A method for example, Patent Document 1
  • This method substantially reduces the amount of solid solution C in steel by forming C in steel as a carbide other than Fe 3C at a temperature higher than the cementite formation temperature, thereby reducing deformation resistance and deformability.
  • the purpose is to suppress the formation of semenite and thus pearlite, which inhibits, while also significantly increasing the amount of pro-eutectoid ferrite and significantly improving cold workability.
  • the spheroidizing annealing treatment can be omitted, the tensile strength of the obtained steel wire reaches only 500 MPa, so that the molded product obtained by cold heading can be used.
  • tempering treatment such as quenching and tempering is required.
  • the cost is increased, for example, the addition of V, which is a relatively expensive alloy element, to generate C in steel as a carbide other than Fe3C.
  • Patent Document 3 proposes a technology that can omit quality processing, and have proposed this as a new invention.
  • ferrite with an average grain size of 1 to 2 m or less in the cross section perpendicular to the rolling direction A steel with a microstructure as the main phase can be manufactured, and without quenching or quenching / tempering treatment, the mechanical properties of the steel sheet are 70% or more in drawing and 800% in tensile strength.
  • the inventor of this application has ensured the excellent properties and effects of the steel obtained by this technology, and further improved the strength while maintaining a high level of cold workability. We have been studying measures to make this happen.
  • the target value of the proposed tensile strength TS in the proposed invention is not less than 600 MPa (preferably 800 MPa). (MPa or more), preferably greatly exceed them, and maintain as much as possible 65% or more (preferably 70% or more) of the target aperture in the same patent application. It was set that it should exceed these. And specifically,
  • Case 1 T S ⁇ 70 OMPa, and RA ⁇ 65%, and more preferably, RA is increased to 70% or more;
  • the steel of the component system having a substantially cementite-free chemical composition was used as a material, and the technology of the proposed invention was applied thereto.
  • the molten steel discharged from these refining furnaces is further decarburized by vacuum refining in an appropriate vacuum refining furnace.
  • vacuum refining By accelerating the reaction, it is desired to refine the ultra-low carbon steel and to take measures to ensure the cleanliness of the steel by preventing the reoxidation of the molten steel in the production process such as continuous production.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2000-20073
  • Patent Document 2 Japanese Patent Application Laid-Open No. 2003-111
  • Patent Literature 3 Japanese Patent Application No. 2003-43035 Japanese Patent Disclosure
  • the invention is based on the fact that the steel wire or the bar has an average grain size of 500 nm or less in a cross section perpendicular to the longitudinal direction and has a cementite-free ferrite structure. Provide a high-strength steel wire or steel bar with excellent cold workability.
  • the ferrite microstructure in which the C content is less than or equal to the solid solubility limit of carbon in the ferrite phase at the Ael point and the average grain size in the cross section perpendicular to the longitudinal direction of the steel wire or bar is 500 nm or less.
  • the present invention provides a high-strength steel wire or steel bar excellent in cold workability, characterized by having:
  • the ferrite structure must have a C content of 0.010 mass% or less and an average grain size of 500 nm or less in a cross section perpendicular to the longitudinal direction of the steel wire or bar.
  • the present invention provides a high-strength steel wire or steel bar excellent in cold workability characterized by the following characteristics.
  • the average particle size in at least one of the cross sections in any direction is 50 On Provided is a high-strength molded product characterized by having a cementite-free ferrite structure at m or less.
  • the fifth has a ferrite structure in which the C content is less than or equal to the solid solubility limit of carbon in the ferrite phase at the A el point and the average grain size in at least one of the cross sections in any direction is 500 nm or less.
  • a high-strength molded product characterized by the above feature.
  • ferrite tissues having a C content of more than 0.01 to 0.45% by mass and an average grain size of 500 nm or less in a cross section perpendicular to the longitudinal direction of the steel wire or bar are used.
  • a high-strength steel wire or steel bar excellent in cold workability characterized by having a main phase having mechanical properties of a tensile strength of 70 OMPa or more and a drawing of 65% or more. .
  • a ferrite structure having a C content of more than 0.01 to 0.45% by mass and an average grain size of 500 nm or less in a cross section perpendicular to the longitudinal direction of the steel wire or bar is used.
  • a high-strength steel wire or steel bar with excellent cold workability characterized by having mechanical properties of a main phase having a tensile strength of 150 OMPa or more and a drawing of 60% or more. provide.
  • a ferrite tissue having a C content of more than 0.01 to 0'.45% by mass and having an average grain size of 500 nm or less in a cross section perpendicular to the longitudinal direction of the steel wire or bar.
  • a high-strength steel wire or steel bar excellent in cold workability characterized by having a Pickers hardness HV of 285 or more as a main phase.
  • a ferrite structure having a C content of more than 0.01 to 0.45 mass% and an average grain size of at least one cross section of any cross section in an arbitrary direction of 500 nm or less.
  • a high-strength molded product characterized by being a main phase and having a Pickers hardness HV of 285 or more in at least one cross section of a cross section in an arbitrary direction.
  • the C content is more than 0.01 to 0.45 mass%
  • Provide high-strength molded products that have a ferrite structure with an average grain size of 50 O nm or less in at least one cross section of the surface and a tensile strength TS of 90 O MPa or more. I do.
  • a coil-shaped steel wire or steel is characterized in that, in a region of 90% or more of the area of the C cross section of the material to be rolled, the average crystal grain size is refined to 1.0 tm or less. Provide a line.
  • the ingot, slab, slab, or semi-finished steel product having a cementite-free ferrite structure is subjected to warm working to obtain a material with an average grain size of 3 m or less in a cross section perpendicular to the longitudinal direction. And then cold-worked to form a ferrite structure having an average crystal grain size of 500 nm or less at a cross section perpendicular to the longitudinal direction.
  • a method for manufacturing a steel wire or a steel bar is provided.
  • a steel ingot, slab, slab, or semi-finished steel product whose C content is less than or equal to the solid solubility limit of the carbon in the ferrite phase at the Ael point is subjected to warm working, and A material having an average crystal grain size of 3 m or less at the cross section is prepared, and then cold-worked to form a ferrite structure having an average crystal grain size of 500 rim or less in a cross section perpendicular to the longitudinal direction.
  • high-strength steel wire or steel bar excellent in cold workability manufactured by the manufacturing method of the above 13 and 14 is used for cold forging, cold forging and Z or cutting.
  • the ingot, slab, slab, or semi-finished steel product having a C content of more than 0.01 to 0.45 mass% is subjected to warm working so that it is perpendicular to the longitudinal direction.
  • a material having an average crystal grain size of 3 m or less in the cross section is prepared, and then cold-worked to form a ferrite main phase structure having an average crystal grain size of 500 nm or less in a cross section perpendicular to the longitudinal direction.
  • a method for producing a high-strength steel wire or steel bar excellent in cold workability characterized by being characterized in that: Brief Description of Drawings
  • Fig. 1 is a graph illustrating the relationship between the rolling parameter Z and the average ferrite grain size.
  • Fig. 2 is a diagram showing a diamond type, a square type, and a hole-shaped dimension part of an opal type caliper roll.
  • FIG. 3 is an example of a ferrite structure photograph by SEM of an L-direction cross section of a steel wire rod after warm working in a process of manufacturing steel according to the invention of the present application (in the case of Example 3).
  • Fig. 4 When the cold work rate is converted to industrial strain e and expressed, the tensile strength TS increases with the increase of the cold work rate, and the example and comparative example at that time are shown. 6 is a graph showing the difference between.
  • Fig. 5 When the cold work rate is converted to industrial strain e and expressed, the state of the reduction of the drawing RA with the increase of the cold work rate is shown, as well as between the working example and the comparative example at that time. 6 is a graph showing the difference between the two.
  • FIG. 6 is a graph comparing the quantification of the level values of the tensile strength T S and the squeezing RA and the balance between the tensile strength T S and the squeezing RA between the example and the comparative example.
  • Fig. 7 is a graph comparing the level of tensile strength T S with respect to the C content of a steel wire between an example and a comparative example.
  • Fig. 8 is a graph comparing the level of reduction RA with respect to the C content of a steel wire between an example and a comparative example.
  • Fig. 9 is a photograph showing a state in which a torsion delayed fracture test piece of Ml. 6 pan head screw is set.
  • Fig. 10 When the cold work rate is converted into industrial strain e and expressed, the tensile strength TS increases with the increase of the cold work rate, and it is compared with the example at that time. 7 is a graph showing a difference from the example.
  • cold working 6 is a graph showing a state of a decrease in the aperture RA with an increase in the rate, and showing a difference between the example and the comparative example at that time.
  • Fig. 12 is a graph showing the quantification of the values of the tensile strength T S and the drawing RA and the balance between the tensile strength T S and the drawing RA for the example and the comparative example.
  • FIG. 13 is an example of a ferrite structure photograph by TEM of a cross section in the L direction of a cold-worked steel (steel wire) obtained by the manufacturing method according to the invention of the present application (in the case of Example 2).
  • Fig. 14 is a graph comparing the level of the tensile strength T S with respect to the C content of the steel wire between the example and the comparative example.
  • Fig. 15 is a graph comparing the level of drawing RA with respect to the C content of a steel wire between an example and a comparative example.
  • the main phase of the S crystal structure is ferrite, and the C content exceeds 0.01% by mass and Q: up to 45% by mass.
  • the first feature of the chemical composition of the high-strength steel wire or steel bar excellent in cold workability and the high-strength molded product according to the invention of this application is that the main phase of the metal crystal structure is ferrite,
  • a high-strength steel wire or steel bar having excellent cold workability according to the invention of the present application which is a carbon steel or low-alloy steel having a content of more than 0.01% by mass to 0.45% by mass;
  • the second characteristic of the chemical composition of high-strength molded products is that of high-strength steel wire or rod with excellent cold workability.
  • the chemical composition of steel and high-strength molded products is such that the main phase of the metal crystal structure is substantially cementite-free and the C content is equal to or less than the solid solubility of carbon in the ferrite phase at the Ael point.
  • the C content and the tensile strength TS described in the specification of the invention of this application are determined by giving the content of other component elements. (Eg, Fig. 7 and Fig. 8), as needed, to satisfy the mechanical properties and the like desired for the target application to be manufactured.
  • the lower limit of the C content may exceed 0.01% by mass, and the upper limit of the solubility of carbon in the ferrite phase in Ae may be exceeded.
  • the solid solubility limit of the C content included a metal element such as Cr or Mo, which replaces the-part of 63 elements with this element M to generate Fe (3X) MXC. Even in this case, if the content of alloying elements contained in the steel wire or bar made of low-alloy steel is about the same, it is close to the solubility limit of carbon in the ferrite phase at the Ael point in the component system of carbon steel. It is.
  • the solid solubility limit of carbon in the ferrite phase at the Ael point can be estimated using, for example, a known calculation software “Thermo-c a 1 c” (“Thermo-ca 1 c” is Although the calculation is in the equilibrium state, the cooling conditions during actual manufacturing are not in the equilibrium state, so it cannot be completely estimated.) Further, the metal structure needs to have ferrite as a main phase. In the first place, the crystal structure of the steel wire rod having an average grain size of 3 m or less prepared by warm rolling, which is one of the constituent elements in the method of manufacturing the high-strength steel wire or the bar steel of the invention of the present application, is determined by the inventor. According to the above proposed invention, it should be a steel containing ferrite as a main phase.
  • alloying elements it is not necessary in the invention of the present application to rely on the addition of alloying elements in order to improve the strength of the material when defining the chemical composition. Therefore, there is no need to dare to add elements that promote hardenability improvement, such as Cr and Mo, other similar elements, and solid solution strengthening elements Cu and Ni and other similar elements. In addition, the above alloy elements do not need to be added to reduce manufacturing costs. Is more desirable.
  • the Si content should be less than 1.0% by mass and the Mn content should be lower. It is even more desirable to limit the amount to less than 2.0% by weight.
  • C, Si, and the like are applied to molded products represented by steel wires or steel bars, screws and ports, and ingots and billets.
  • A1 as a deoxidizing agent
  • valuable elements such as Ti, Nb and V as a dispersion precipitation strengthening element
  • the contents of P, S, N, etc., which are treated as harmful impurities, are not specified, but the content of deoxidizing elements should be at a level that is essential for conventional refining and manufacturing technologies.
  • the content of unavoidable impurities should be limited for elements treated as impurities, and should not be particularly limited to ultra-low content. For other valent elements, the content should not be particularly limited. There is no need to include it. This is because the invention of this application can sufficiently solve the problem.
  • a steel having a MPa of not less than 150 MPa, and more desirably 150 OMPa or more can be obtained, and furthermore, a steel whose drawing RA is maintained at a high level according to the tensile strength can be obtained.
  • the C content is It is specified that the temperature is below the solid solubility limit of carbon in the ferrite phase at the A el point. Further, the content of C, which is considered not to generate cementite in a normal low alloy steel component system, is specified to be 0.010% by mass or less.
  • the C concentration (mass%) in the ferrite phase at the A el point is less than or equal to that, so the cementite-free structure is actually formed.
  • the C concentration (% by mass) at which this cementite-free material is actually obtained can be estimated using, for example, known calculation software “T her mo-ca 1 c”. (“T hermo—ca 1 c” is a calculation in an equilibrium state, but the cooling condition during actual manufacturing is not in an equilibrium state, so it cannot be said that it can be completely estimated).
  • a steel material having a cementite night-free ferrite structure having the above-described high strength and excellent cold workability (strength and workability).
  • High-strength steel with excellent balance of steel can be designed.
  • the Si content should be less than 1.0 mass%. It is even more desirable to limit the Mn content to 2.0% by mass or less.
  • the emphasis is on cement-free night-free steel. Therefore, it is not necessary to depend on the addition of alloying elements when defining the chemical composition. Therefore, the addition of elements that promote hardenability improvement, such as Cr and Mo, and other similar elements, and the addition of solid solution strengthening elements Cu and Ni and other similar elements are intentionally added. No need. In addition, it is desirable not to add the above-mentioned alloy element from the viewpoint of reducing the production cost. Therefore, it is desirable that none of the above elements have a content that is inevitably mixed in the steel refining and smelting process.
  • the element effective for precipitation strengthening is used. Elemental Ti, Nb, and other alloying elements are not enough to be added. This is because the cementite-free component system disclosed in the present application can secure a sufficient tensile strength, which is useful for reducing the production cost.
  • the C content of the steel (steel wire or bar and molded product) according to the invention of this application is designed to be basically cementite-free. Therefore, the standard structure of the steel is always a ferrite structure.
  • C, Si, Mn, and Cr are required for molded products typified by steel wires or bars, screws and bolts, and ingots and billets.
  • elemental elements other than Ni, such as A1 as a deoxidizing agent valuable elements such as Ti, Nb and V as dispersion-precipitation strengthening elements, and P which is usually treated as a harmful impurity , S, N, etc., their contents are not stipulated.However, for deoxidizing elements, the levels required for conventional refining and production technology should be secured. Should be limited to the unavoidable content, and should not be limited to an extremely low content. Other valuable elements do not need to be contained, although the content is not particularly limited. This is because the invention of this application can sufficiently solve the problem.
  • the tensile strength TS is at least 70 OMPa, and the tensile strength TS is 100 OMPa or more, and more preferably, 150 OMPa or more depending on the application.
  • the drawing RA is also maintained at a high level in order to ensure ductility according to each level of the tensile strength TS. is there.
  • this tensile strength TS and drawing The balance with RA is, as mentioned above, the balance as shown below:
  • Case 1 T S ⁇ 700 MPa and RA ⁇ 65%, and more preferably, further improve the level of the aperture RA to obtain T S ⁇ 700 MPa and RA ⁇ 70%,
  • a steel wire or a steel bar can be supplied to a destination according to an application.
  • Such provisions are made in order to improve the yield for processing and to supply molded products of a quality level that has not been realized before, when processing molded products.
  • the steel wire or bar steel with high strength and excellent ductility of the invention of this application is used for applications. Proper supply together will dramatically increase the processing yield.
  • the average particle size of the ferrite is reduced to 200 nm or less, the combination of the tensile strength TS and the drawn RA of the steel according to the invention of the present application can be more easily and more highly leveled. It is desirable because it can be obtained stably.
  • the average grain size in at least one of the cross sections in any direction shall be considered to be almost the same as the average grain size in the C direction cross section of the wire or bar. Can be.
  • the specification expressed in hardness as a strength characteristic in place of the tensile strength TS is specified. It is desirable that the hardness is 285 or more in the picks hardness HV. If the hardness of pits is HV 2 285 or more, This is because a tensile strength of about 90 OMPa is secured. On the other hand, in the molded product represented by the screw or porto according to the invention of this application, it may not be easy to prepare a tensile test piece depending on the shape. Therefore, the specification of hardness should be sufficient as a mechanical property instead of tensile strength.
  • the provision of hardness as an alternative to tensile strength plays a more important role in evaluating the characteristic level of actual products. More preferably, the molded article has a Vickers hardness HV of at least 300, which is equivalent to a tensile strength TS of about 100 OMPa.
  • the basic features of the manufacturing method according to the invention of the present application are as follows. First, as a method of manufacturing a steel wire or a steel bar excellent in cold workability according to the invention of the present application, a predetermined material is used. Is subjected to warm working under appropriate conditions, and a fine-grained structure steel is prepared by this warm working.
  • the crystal grain size of the material obtained here is desirably as small as possible. Specifically, the average grain size at the cross section perpendicular to the longitudinal direction (cross section in the direction C) of the material obtained by warm working is 3 m. It must be: Next, it is said that such a material is subjected to cold working under appropriate conditions.
  • a desirable warm working condition for a predetermined steel ingot, a piece or a billet or a steel material is as follows. It should be in the range of ⁇ 800.
  • the plastic strain introduced into the material and remaining should be ensured.
  • the amount of plastic strain can be obtained by calculation using a known three-dimensional finite element method (the value is represented by “ ⁇ ”), and it is preferable that ⁇ is 0.7 or more.
  • Such warm working conditions were adopted in order to refine the crystal grains as a method of realizing high strength of the steel without substantially utilizing the strengthening mechanism by phase transformation.
  • FIG. 1 shows an example of the relationship between the rolling condition parameter Z and the average ferrite grain size. That is, FIG. 1 shows that by controlling the rolling so that Z ⁇ l1, a fine grain structure having an average ferrite grain size of 1 am or less can be obtained.
  • the hot rolling temperature to satisfy Z ⁇ 11, it is possible to reduce the average ferrite grain size of the material to less than 3 m.
  • any of warm rolling and warm forging may be adopted, and in this case, a plurality of buses (in the case of warm forging, a plurality of forging schedules are used) in multiple directions.
  • the processing is desirable because the plastic strain in the material can be made uniform.
  • desirable cold working conditions to be performed in advance are: It is desirable that the processing temperature is less than 350 ° C. If a higher temperature is reached during cold working due to the heat generated during processing, the increase in tensile strength decreases, which is not desirable. Next, it is necessary to secure the residual strain introduced into the material by cold working according to the desired tensile strength. From this viewpoint, it is desirable to perform the cold working so that the plastic strain ⁇ obtained by the three-dimensional finite element method is at least 0.05.
  • the cold-worked structure of the crystal exhibits a form elongated in the working direction, and the grain size in the cross section in the C direction with respect to the working direction is also reduced, so that an increase in tensile strength is secured.
  • the reduction in the aperture RA is kept small.
  • any of the well-known cold drawing method and cold rolling method may be adopted as the cold working method.
  • the cold rolling method it is preferable to use a known combined roll method. If the form of the steel produced by cold working is steel wire or steel bar, among JISG 359 9 carbon steel wires for cold heading, forming that requires particularly high strength and good cold workability is required. It can also be used for JISG 3505 hard steel wire, which is a steel type with a relatively low C content area, which requires particularly high strength and good cold workability. it can.
  • the main phase of the metal crystal structure is ferrite, and the C content is in a wide range from a carbon content of more than 0.01 mass% to 0.45 mass% in a carbon steel or a low alloy steel.
  • Example 1 and Example 2 are partially different in the manufacturing process of the high-strength steel wire or steel bar according to the invention of the present application, and Examples 1 and 2 and Example 3 However, the chemical composition is also different. Therefore, Examples 1 and 2 and Example 3 separately describe the test method and test results.
  • Example 1 and Example 2 were tested as follows. Steel having the chemical composition shown in Table 1 was smelted using a vacuum melting furnace and formed into an ingot.
  • This chemical composition is, for example, the content of Si: 0.10 mass in the chemical composition specified in SWRCH5A belonging to the carbon steel wire for cold heading of JISG 357. %, The content of which exceeds 0.3% by mass. However, it is characteristic that the C content is as low as 0.0245% by mass.
  • the steel ingot obtained above was formed into an 80 mm square bar by hot forging.
  • the metal structure of these bars is the main phase of ferrite, and the average grain size of ferrite in the cross section in the C direction was about 20 m or less.
  • a rolling material was sampled from each of the above 80 mm square bars, and formed into 18 mm square by multi-pass multi-pass caliber rolling in warm water. After cooling, a steel bar was prepared.
  • the warm rolling is for preparing a material for a steel wire or a steel bar according to the present application, and the material obtained by the warm rolling has an average grain size of 3 iim in a cross section perpendicular to the longitudinal direction. The test was performed under the following conditions.
  • the one-pass warm rolling with the opal-type force ripper roll a 24 mm square bar is rolled with the oval-type caliper roll, so that the opposite side length of the cross-section in the C direction of the material before rolling is 24 mm.
  • the area reduction rate calculated from the hole dimensions at this time is quite large at 38%. Therefore, the one-pass warm rolling with the oleno type caliber roll is a condition for further promoting the refinement of the ferrite grain size in the 18 mm square bar after the completion of the warm rolling.
  • the 18 mm square steel bar prepared by the above-mentioned warm rolling method was reduced in diameter by cutting to form a steel wire rod having a diameter of 6.0 mm.
  • Omm ⁇ the reason why the diameter was reduced by cutting from 18 mm square to 6.
  • Omm ⁇ is as described below.
  • Ml. 6 pan head screw specified in JIS Bill 1 was used for steel wire.
  • the diameter of the effective section of the thread is 1.27 ⁇
  • the diameter is 1.3 ⁇ by cold drawing with a target drawing rate of 95% or cold rolling with a target total area reduction of 95%. It is because it is the material which can be obtained.
  • test material for accuracy of 6. ⁇ was collected and tested for the following items.
  • Hardness measurement test by Vickers hardness tester It is effective to confirm the correlation with tensile strength as one of the strength characteristics and when it is difficult to collect tensile test specimens. This was performed based on the method specified in JIS Z2244.
  • Measurement test of ferrite grain size (d) by microscopic test Prepare an appropriate microscopic specimen from each test material and determine the average grain size of ferrite, which constitutes the main phase in the microstructure of the metal crystal, Measure the average ferrite grain size in the cross section perpendicular to the longitudinal direction (corresponding to the longitudinal direction of the above 18 mm square bar) (cross section in the C direction). At that time, the microstructure in the L-direction section was actually observed, and the average ferrite grain size in the C-direction section was determined.
  • Table 3 shows the test results of the above-mentioned warm rolled materials.
  • the steel wire obtained by this warm rolling is a low-carbon steel having a C content of 0.0245% by mass, without any special strengthening elements added, and even after being warm-rolled. Regardless, the tensile strength TS is as high as 70 MPa, and at the same time, an extremely high level of 18.6% is achieved at 78.6%.
  • Example 1 using the 6.0 mm ⁇ steel wire rod after collecting the above 6.0 mm accuracy test material, in Example 1, cold drawing was performed, and in Example 2, cold rolling was performed. In both cases, tests were conducted to manufacture steel wires by cold working from 6. ⁇ to 1.3 mm ⁇ .
  • the starting diameter of the wire drawing material is 6. 6. ⁇
  • wire drawing from 6.0 mm to 1.3 mm was easily performed without any spheroidizing annealing or other softening treatment. .
  • test materials for accuracy as drawn were collected.
  • the accuracy test method is as follows, and 1) 2) 3) are as described above.
  • a steel wire with a wire diameter of 1.3 ⁇ is preformed by header processing in the manufacturing process of M 1.6 small screw specified in JIS Bill 1, and then a predetermined A cross-shaped recess (a cross-shaped recess for tightening this screw with a dry par) is formed by cold heading.
  • This test is to observe the condition of cracks in this recess during molding with a 10x magnifier.
  • the occurrence of recess cracking varies greatly depending on the recess shape of the machine screw.However, the cross-shaped recess forming of Ml. 6 pan-head screw is extremely severe forging and is considered a practical test in this specification.
  • Torsion torque test of small screw From a steel wire with a wire diameter of 1: 3 mm, a screw intermediate formed by forging a recess with a recess as described above was formed by cold drawing to form a M1.6 pan. Prepare machine screws. Next, this is measured by an appropriate torque measuring device according to the method specified in 5.4 “Torsion test” of JISB 1060 “Mechanical properties and performance of carburized, quenched and tempered metal thread rolling screws”. Increase torque until screw breaks. The torque value (torque at break (kgf ⁇ cm)) required to cause blasting was measured. The purpose of this test is to evaluate the "torsional strength" which is one of the mechanical properties of fasteners such as screws and ports. Hereinafter, the same applies in this specification. For a Ml. 6 pan head screw, the breaking torque is 3. Desirably, it is 0 kgf ⁇ cm or more.
  • Table 5 shows the test results of Example 1 above.
  • Example 1 The test results in Table 5 show the following. That is, the 1.3 ⁇ steel wire obtained in Example 1 was a low-carbon steel having a C content of 0.0245% by mass, without the addition of a special strengthening element, and quenching and tempering. Although it has not been subjected to any heat treatment or any softening treatment, its tensile strength TS is remarkably high at 1567 ⁇ a, and the drawing RA is also at a considerably high level of 60.2%. This is because, as shown in Table 3, the material is already extremely high in tensile strength TS of 702 MPa due to warm rolling, and the Vickers hardness HV is also extremely high at 355,
  • the drawn RA is 78.6%, which is a fine ferrite microstructure steel (average ferrite grain size in the cross section in the C direction is 0.7), which has already reached a high level. This is because cold working is performed with a total reduction of area of 10%.
  • the steel wire of Example 1 is a low-carbon steel
  • the strength and the high ductility are imparted because the crystal grains of the steel wire are composed of a fine ferrite main phase.
  • the 1.3 ⁇ steel wire of Example 1 had an average ferrite grain size in the cross section in the C direction of 182 nm, and exhibited a form in which the bump and the structure were stretched in the direction of cold drawing. Ferrite main phase.
  • the average ferrite grain size in the cross section in the C direction of the steel wire prepared by warm rolling is 0.7 ⁇ (Table 1).
  • the starting diameter of the material for rolling is 6. ⁇ , that is, rolling from 6. ⁇ to 3.3 ⁇ ⁇ in 8 passes in the first process, and from 3.3 ⁇ in 10 passes in 2
  • the steel wire was manufactured by rolling from 1.8 mm ⁇ i> to 1.3 mm ⁇ in five passes of the third step.
  • the material temperature during rolling was below 200 ° C.
  • cold rolling from 6. Omm * to 1.3 ⁇ could be easily performed without any spheroidizing annealing or other softening treatment.
  • 1.8mm (f) total area reduction: 91.0%)
  • 1.3 ⁇ total area reduction: (95.3%). I took it.
  • the accuracy test method is as described below.
  • Example 2 The difference between the production conditions of Example 2 and that of Example 1 is that cold rolling was performed instead of cold drawing. All other conditions are the same.
  • the tensile strength TS was 922 MPa at a wire diameter of 3.3 ⁇ (total area reduction rate: 69.8%) and a wire diameter of 1.
  • 8 mm total area reduction: 91.0%
  • the hardness HV of the powder is 328, which is an extremely high level at a wire diameter of 1.3 ⁇ (total area reduction: 95.3%).
  • Example 2 (cold rolling method) has 328
  • Example 1 (cold wire drawing) has It is 355 ', and it can be seen that when the other conditions are the same, the hardness increase is slightly larger in the case of cold drawing than in the case of cold rolling.
  • the cold working method for the material is either the cold drawing method or the cold rolling method, regardless of the chemical composition of the material (steel wire) immediately before cold working.
  • the state of the crystal structure especially the ferrite main phase structure in which the average ferrite grain size in the C-direction cross section is the same, and the tensile strength TS and the drawing R You can see that it can be obtained. Further, even without cold rolling, without spheroidizing annealing, the torsional rupture torque of a Ml. 6 threaded screw is 2.92 kgf ⁇ cm, which is close to its desired level of 3. Ok-gf ⁇ cm. High torsional strength is exhibited.
  • Example 3 within the scope of the invention of this application, the following test was conducted.
  • a commercially available 13 mm ⁇ steel wire that belongs to SWRCH 5 A has the chemical composition shown in Table 8, and is manufactured by hot rolling.
  • the composition of this steel wire rod is 0.03% by mass of carbon C, and is similar to the composition of the steel used in Examples 1 and 2.
  • the Si content of the test steel of Example 3 was 0.03% by mass, which is different from the Si of Example 1 and 2 of 0.30% by mass, and the Si content of the SWRCH5A was specified.
  • the above 13 mm hot rolled steel wire is rolled at 450.
  • a steel wire rod of 6 ⁇ ⁇ was prepared by multi-direction and multi-pass warm rolling using caliper rolls.
  • the warm rolling method was applied to the test steel wire rods for Examples 1 and 2.
  • a force river roll rolling was performed by appropriately combining a diamond type, a square type, and an opal type.
  • a test material for accuracy was sampled from the above 6 mm ⁇ steel wire rod obtained by the warm rolling in this way, and the following items were tested.
  • the 6.0 mmc ⁇ steel wire rod after the collection of the test material for accuracy was continuously subjected to the test of Example 3 (as described above).
  • Table 9 shows the test results.
  • the test results in Table 9 show the following.
  • the microstructure of the metal crystal of the steel wire rod of Example 3 was mainly composed of ferrite, and the ferrite grain size was in the C direction as shown in the microstructure photograph in the L direction cross section by SEM (scanning electron microscope) in Fig. 3.
  • the average ferrite grain size in the cross section is as fine as 0.8 xm. Therefore, despite being a low-carbon steel with a C content of 0.03% by mass, a high tensile strength TS of 8 17 MPa was secured, and a reduction of 8 A high level of properties of 0.0% was obtained, indicating that the material had an excellent balance between strength and formability.
  • Example 3 a test was conducted in which a steel wire was manufactured by cold rolling as follows using a 6.0 mm steel wire rod prepared by the warm working as described above as a raw material.
  • a steel wire was manufactured by cold working to 1.3 ⁇ in accordance with the first to third steps of the cold rolling in Example 2 shown in Table 6.
  • test materials for accuracy 2. ⁇ (87.8%), 1. ⁇ (total area reduction: 91.0%) and 1.3mm (i) (total area reduction: 95.3%)
  • the steel wire test material as it was cold rolled was sampled.
  • Example 3 the tensile strength TS of the steel wire was 114 OMPa at a wire diameter of 1.8 ⁇ (total area reduction: 91.0%) and a wire diameter of 1.3 ⁇ (total area reduction: 95.3). %), which is a high level of 1202 MPa. And the aperture RA at this time is each smell 72.3% and 70.2%. In addition, the hardness HV of the pipes reaches an extremely high level of 310 at a wire diameter of 1.3 ⁇ (total area reduction: 95.3%). Thus, the average ferrite grain size in the section in the C direction is as fine as 186 m.
  • Example 3 Comparing the tensile strength TS and the drawn RA at 1.3 mm ⁇ i) (total area reduction 95.3%), where the wire diameter is the same, the Si content is as low as 0.03 mass%. Although the tensile strength TS of Example 3 is lower than that of Example 1 in which the tensile strength is 0.30% by mass (Example 3:
  • Example 3 70.2%, Example 1: 6
  • Example 1 0.0245% by mass
  • the test material for accuracy is a normal hot-rolled material, that is, a steel wire material that has been rolled at the A3 transformation point or higher. This is a manufacturing condition of a steel wire rod outside the scope of the manufacturing method of the invention of this application. Therefore, the average grain size of the ferrite, which is the main phase structure of the metal crystal, in the cross section in the C direction is about 16 to 20 m, and the fine grain structure is not formed. For this reason, the drawn RA is excellent at a high level of 80.1 to 85.9%, but the tensile strength TS is 350 to 550 MPa, and the C content tested in Examples 1 to 3 was low. 0.0245 to 0.03 mass%, which is remarkably lower than 817 MPa (see Table 9) of the steel wire manufactured by warm rolling.
  • the cold rolling conditions are the same as in Example 2 above (see Table 6; rolling temperature is less than 200). In this cold rolling process, for accuracy, 3.3 ⁇ (total wire reduction area: 69.8%), 2.3 ⁇ (total wire reduction area: 85.3%) and 1.3 ⁇ ( Cold-rolled steel wire test material with a total wire reduction of 95.3%) was sampled.
  • Test C Test material Cold working Industrial annealing Tensile strength Drawing Recess forming Torsion wire diameter Total area reduction Strain and property Breaking torque
  • Yes-One crack-Cold work total area reduction indicates the total area reduction by cold drawing or cold rolling.
  • test materials are steel wire test materials obtained in the test process of the comparison! L 1-3, which are out of the scope of the invention of this application, and the C content is in the level of 0.04-0.1.8%. It is.
  • the steel wire prepared by hot rolling is subjected to cold drawing or cold rolling, and as the total area reduction increases, the tensile strength TS increases and the drawing RA decreases. (Shown in Figures 4 and 5 below). It can be seen that the total area reduction rate for the tensile strength TS to exceed 100 OMPa is almost 95.3% corresponding to the wire diameter of 1.3111111 ( ⁇ in Comparative Examples 2 and 3.
  • Approximate increase 600 to 650 MPa
  • the reduction of RA is from 80 to 85% in the material, from 1.3 to ⁇ in the diameter of steel wire to less than 65 to less than 70% ⁇ in the steel wire. It is about 20%, which is larger than that in Examples 1 to 3.
  • FIG. 6 further illustrates the relationship between the tensile strength TS and the drawing RA for Examples 1 to 3 and Comparative Examples 1 to 3.
  • the reduction amount of the drawing RA due to the increase in strength is significantly smaller than that of the comparative example, and the level of the drawing RA after the reduction is higher than the level of the comparative example.
  • a very great advantage was confirmed.
  • high strength and ductility are maintained at a considerably high level, and a wire excellent in strength-ductility balance can be obtained.
  • the torsional rupture torque was about 2.3 kgf Xcm for Comparative Example 1 and Comparative Example 2 in which recess cracking did not occur, and was about 2.3 kgf Xcm. It has not reached 3.0 kg f Xcm.
  • the C content Is made of low carbon steel of approximately 0.03% by mass, and has a tensile strength TS of a high level of, for example, 1000M Pa or more, and a low drawing RA, which can be maintained at a considerably high level of, for example, 65% or more. It can be seen that a steel wire with excellent forging properties can be obtained in the state of cold working without spheroidizing annealing.
  • Fig. 7 shows the level of the tensile strength TS with respect to the C content of the steel wire
  • Fig. 8 shows the stratified graph of the level of the drawn RA with respect to the C content of the steel wire between the example and the comparative example.
  • the wire diameter is 1.3 mm (the industrial strain is 3.06) is shown. According to this, it can be seen that in the example, even if the C content is relatively lower than that of the comparative example, the tensile strength TS is high and the drawn RA is equal to or higher than that.
  • a raw screw and a carburized hardened screw manufactured from a commercially available SWCH 16 A steel wire manufactured according to a conventional technique were set as a comparative example 4.
  • This screw was an M 1.6 pan screw and its chemical composition is shown in Table 14.
  • This method of manufacturing Ml. 6 pan head screws is based on the prior art, in which a steel wire is manufactured by hot rolling, and then cold drawn by a conventional technology to manufacture a 1.3 ⁇ steel wire. After being subjected to spheroidizing annealing to improve cold forging, cold forming and rolling to form Ml. 6 pan-head screws (raw screws), and carburizing for raw screws There are two types of Ml. 6 small screws (carburized and quenched screws) that have been subjected to tempering treatment and have a given strength.
  • the main phase of the metal crystal structure in the example is substantially cementite-free, the C content is not more than the solid solubility limit of carbon in the ferrite phase at the Ael point, or the C content is not more than 0.010% by mass.
  • Each steel having the chemical composition of No. 1 to 5 shown in Table 16 was smelted using a vacuum melting furnace and formed into steel ingots.
  • the obtained steel ingot was formed into an 80 mm square bar by hot forging. These steel bars gold
  • the microstructure was composed of ferrite, and the average grain size of the ferrite in the cross section in the C direction was about 20 or less.
  • a rolling material was sampled from each of the above 80 mm square bars, formed into 18 mm square by multi-pass multi-pass caliper rolling in a warm state, and water-cooled to prepare a steel bar.
  • This warm rolling is for preparing a material for a steel wire or a steel bar according to the invention of the present application, and the material obtained by the warm rolling has an average crystal grain size in a cross section perpendicular to the longitudinal direction of 3 or less.
  • the test was performed under the following conditions.
  • the one-pass warm rolling by the opal type caliber roll is a condition for further promoting the refinement of the ferrite grain size in the 18 mm square bar after the completion of the warm rolling.
  • Ml. 6 pan head screws specified in JIS Bill 1 for steel wire use were used.
  • the diameter of the effective section of the thread is 1.27 ⁇
  • a diameter of 1.3 ⁇ can be obtained by cold drawing with a target drawing rate of 95% or cold rolling with a target total area reduction of 95%. This is because it is a material that can be used.
  • the choice of Ml. 6 pan head screw is because, in order to forge a cross-shaped recess (recess for applying torque with a screwdriver) at the head, extremely excellent cold forging is required. This is to evaluate whether or not it has particularly excellent cold headability by the cross-shaped “recess forming test” of Ml. 6 pan head screw described later.
  • A0 group test material J consisting of five types corresponding to component Nos. 1 to 5 in Table 16. The following items were tested.
  • Table 17 shows the test results of the warm-rolled material.
  • the A0 group test material is a warm material that satisfies the preparation conditions (manufacturing conditions) for the material (steel wire material) in the components of the method for manufacturing a high-strength steel wire or steel bar excellent in cold workability according to the invention of this application.
  • the preparation conditions manufacturing conditions
  • the chemical composition of the material is metallographically a cementite-free carbon steel component. Therefore, the microstructure of the metal crystal is cementite-free, and fine grains having an average ferrite grain size of 0.7 to 0.9 mm are obtained.
  • the material is The method for producing a high-strength steel wire or a steel bar excellent in cold workability according to the invention of the present application, and what is obtained by the method can be performed by subjecting a material having such material characteristics to cold work. Things. In particular, it can be seen that even in an ultra-low carbon steel having a C content of 0.0014 to 0.0109 mass% or less, the bow I tensile strength has a high level of 600 MPa or more.
  • Examples 1 to 5 (Steel wire production test by cold drawing) '' For components Nos. 1 to 5 (see Table 16) prepared by warm rolling described above. Five types of 6. ⁇ steel wire rods were used as materials, and a test was conducted to produce steel wires by cold drawing to 1.3 mm ⁇ (hereinafter referred to as “Examples 1 to 5J”). The conditions for cold drawing in these examples are all as follows: normal temperature 6. 6. ⁇ steel wire (as described above, processed to 18 mm ⁇ by warm rolling, then 6. As shown in Table 18, a steel wire rod machined to a diameter of 0 mm ⁇ was sequentially drawn with drawing dies of dies No. l to No. 17 to produce a steel wire of 1.3 mm ⁇ . The material temperature during drawing was less than 200. Table 18
  • the starting diameter of the wire drawing material is 6.0 ⁇
  • the wire drawing process of all of these examples from 6.0 mm ⁇ to 1.0 mm without any spheroidizing annealing or other softening treatment.
  • the wire could be easily drawn down to 3 mm.
  • a test material for as-drawn accuracy hereinafter referred to as “ ⁇ 1 group test material j” was collected at each stage.
  • a cold forming test for Ml.6 pan head screws was conducted. The following tests were performed on the test materials “A1 group test materials” of Examples 1 to 5.
  • Torsion torque test of small screw From a steel wire with a wire diameter of 1.3 mm, the screw intermediate formed by forging the recess as described above is cold-formed to form a screw section, and the M1.6 pan is used. Prepare machine screws. Next, this is measured by an appropriate torque measuring device in accordance with the method specified in 5.4, “Torsion test” of JISB106, “Mechanical properties and performance of metric thread rolling screws subjected to carburizing, quenching and tempering”. Increase the torque until the screw breaks. The torque value (torque at break (kgf ⁇ cm)) required to cause blasting was measured. The purpose of this test is to evaluate the "torsional strength" which is one of the mechanical properties of fasteners such as screws and ports. Hereinafter, the same applies in this specification. For Ml. 6 pan head screws, the breaking torque is 3.
  • it is not less than 0 kgf ⁇ cm.
  • Torsion delay fracture test of small screw M 1.6 pan small screw prepared from steel wire with a wire diameter of 1.3 mm ⁇ was measured at 70% of the breaking torque value obtained in the breaking torque test. As shown in the photograph of FIG. 9, the test piece was closed and set in a twisted state, and the delayed rupture resistance was evaluated based on whether or not torsional fracture occurred within 72 hours. The number of torsion test pieces set is 10. Note that this torsional delay fracture test was performed only for The test results are shown in Tables 19 and 20. Bugugpur A1 Le1 A
  • Test Component C Tensile Strength Drawing Material Name Diameter Total Area Reduction Strain
  • the A1 group test materials are test materials collected from the steel wires obtained by the examples falling within the scope of the invention of this application. More specifically, the A1 group test material has an extremely low C content (c: 0.0014 to 0.0109%), and as described above, is a cementite-free fine ferrite crystal (average particle size d ⁇ 0.9 im) and tensile strength * ⁇ For materials (steel wire) with high levels of S and drawing RA and excellent balance
  • the tensile strength TS changes from the 635-795 MPa level of the material to a total wire reduction area of 87.8% to a level of 1070-1252 MPa, and the total wire reduction area of 91.0%. To 1142 to 1322MPa level, and the total wire reduction area
  • the tensile strength TS of the material is already at a high level of 635 to 795 MPa, and even with a slight strain, the tensile strength TS is further increased. It can be seen that it increases.
  • the diameter of the material immediately before cold drawing (steel Since the diameter of the wire was set to 6.0 ⁇ , this was set to a large value; g, so that even with a thick wire diameter of 5.5 mm or more, a steel wire exceeding 800 MPa could be manufactured. Is possible, at which time the aperture is kept above 75%. From the results of the above test, Fig. 12 shows the relationship between the tensile strength TS and the drawing RA.
  • the high-strength steel excellent in cold workability according to the invention of the present application described above is a steel wire which is not subjected to a tempering treatment such as quenching and tempering while being in a state of cold drawn.
  • a tempering treatment such as quenching and tempering while being in a state of cold drawn.
  • the crystal structure of the steel wire having such excellent material properties is a cementite-free ferrite exhibiting a morphology of a pan-boost structure in the direction of cold drawing, and has a wire diameter of 1.
  • the average ferrite grain size in the C direction cross section of a 3 mm ⁇ steel wire is ultrafine grains of 138 to 175 nm (see Table 20).
  • Example 13 illustrates a TEM (transmission electron microscope) structure photograph of Example 2.
  • the average ferrite grain size is 150 nm.
  • the ferrite grain size will be examined from the measured values of the grain size before and after the cold working.
  • the average ferrite grain size in the cross section in the C direction of the steel wire prepared by warm rolling was 0.8 m (see Table 17).
  • the Ml.6 pan head screw formed from such a steel wire having excellent cold forging properties by cold working of cold forging and cold rolling has a torsional fracture torque of almost 3.0. It can be seen that it has a high torsional strength of kg f ⁇ cm.
  • Example 6 to 9 (Steel wire production test by cold rolling) Similarly, for components Nos. 1 to 4 (see Table 16) prepared by the above-described warm rolling, Four types of 6. ⁇ steel wire rods were used as raw materials, and cold rolling was performed to draw them to 1.3 mmci) to produce steel wires (hereinafter referred to as “Examples 6 to 9”). ⁇ In Examples 1 to 5, the cold-rolled warm-rolled steel wire was used, whereas in Examples 6 to 9, the hot-rolled steel wire was cold-rolled. The manufacturing method of the wire is different. The conditions for this cold rolling are all as follows. As shown in Table 21, the 6 ⁇ ⁇ steel wire rod at room temperature (steel rod processed to 18 mm ⁇ by warm rolling and then to 6.0 mm ⁇ as described above) Process-Cold rolling was performed by each of the compound rolls in the third process. Table 21
  • the starting diameter of the rolling material is 6. ⁇ , that is, rolling from 6. ⁇ to 3.3 ⁇ in 8 passes in the first process, and from 3.3 ⁇ in 10 passes in the second process to 1.8
  • the steel wire was rolled to a diameter of mm ⁇ and then rolled from 1.8 ⁇ to 1.3 ⁇ in five passes of the third step.
  • the material temperature during rolling was below 200 ° C.
  • cold rolling from 6.0 mm ⁇ to 1.3 mm could be performed without any spheroidizing annealing or other softening treatment.
  • Example 9 the as-rolled steel wire test material (hereinafter referred to as “ ⁇ 2 group test material J”) was sampled at the 4th stage.
  • Test Component C Test Material Wire Diameter Tensile Drawing Material Name Total Area Reduction Strain
  • Example 8 3 0.0098 895-Example 9 4 0.0109 999
  • Test Component C Test Material Wire Diameter Tensile Strength Drawing Material Name Total Area Reduction Strain
  • Example 8 3 0.0098 1001 76.9
  • Example 9 4 0.0109 1094 78.5
  • Table 23
  • Examples 6 to 9 differ from those of Examples 1 to 5 in that they were processed by cold rolling instead of the cold drawn wire.
  • the material properties of the steel wire thus obtained are also shown in FIGS. 10, 11 and 12 above.
  • the tensile strength TS of the obtained steel wire also increased significantly with the increase in the total area reduction by cold rolling.
  • Example 7 and 8 having such a material characteristic level, the torsional rupture torque was almost 3.0 even after forming into a Ml. 6 pan head screw and without tempering treatment such as quenching and tempering. Excellent high torsional strength of kg f ⁇ cm.
  • the comparison between the results of Examples 1 to 4 and the results of Examples 6 to 9 shows that the method of manufacturing a high-strength steel excellent in cold workability according to the invention of the present application can be performed by using Steel wire rod It can be seen that the cold working method for W 200 may be either the cold drawing method or the cold rolling method.
  • Comparative examples were divided into a first group and a second group.
  • Ingredient Test destination Ingredient corresponding Chemical composition (% by mass)
  • the B0 group test material is a test material for authenticity of the material to be subjected to the cold working performed in Comparative Example 13.
  • the B0 group test material is a material (steel wire) manufactured by hot rolling, which is a condition for preparing a material in a method of manufacturing steel outside the scope of the invention of the present application. Therefore, the average grain size of the ferrite, which is the main phase structure of the metal crystal, in the cross section in the C direction is 16-20 m. This indicates that the average ferrite and grain size (0.7 to 0.9 m) of the material used as the steel wire in Examples 1 to 9 are extremely large.
  • the drawing RA is excellent at a high level of 80.1 to 85.9%.
  • the tensile strength TS is 350 to 550 MPa in spite of such a high C content, and compared to the tensile strength TS of the steel wire rod used in Examples 1 to 9: 635 to 795 MPa. It turns out that it is extremely low.
  • a steel wire cold-worked to 1.3 ⁇ by cold drawing or cold rolling was prepared using the 6.0mm ⁇ hot-rolled steel wire rod after sampling the B0 group test material. did.
  • hot-rolled steel wire of component No. 7 (equivalent to SWCH10A) and component No. 8 (equivalent to SWCH18A) were cold-rolled to produce steel wires.
  • the cold rolling conditions are the same as in Examples 6 to 9 (see Table 21. Rolling temperature is less than 200 ° C). In this cold rolling process, 3.3 mm ⁇ (total wire reduction: 69.8%), 2.3 mm ⁇ (total wire reduction: 85.3%) and 1 A cold-rolled steel wire test material of 3 ⁇ (total wire reduction: 95.3%) was sampled. This test is referred to as “Comparative Example 2” and “Comparative Example 3”, respectively. As described above, the test materials of Comparative Examples 1 to 3 were collectively referred to as “1 group test materials”. The following tests were performed on these test materials.
  • the B1 group test material is a steel wire obtained in the test process of Comparative Examples 1 to 3 , which is out of the scope of the invention of this application. It is a test material with a C content of 0.04 to 0.18 mass%.
  • a material (steel wire) prepared by hot rolling is subjected to cold drawing or cold rolling, the tensile strength TS increases as the total area reduction increases, and the drawing RA Decreases.
  • the total reduction in area for the tensile strength TS to exceed 100 OMPa is achieved at 95.3% corresponding to the wire diameter of 1.3111111 (
  • the aperture RA at this time has dropped to 64.4 to 66.2%.
  • the reduction from the material of the squeezed RA is about 20%, from 85.9 to 83.0% ⁇ 64.4 to 62.5%, and the reduction is remarkably large.
  • the level of the drawn RA value after the drop is considerably lower than the drawn RA: about 70 to 75% when the tensile strength TS exceeds 100 OMPa in Examples 1 to 9 (see FIG. 12). It is at the standard. _
  • FIG. 14 shows the level of tensile strength TS with respect to the C content of the steel wire for a wire diameter of 1.3 ⁇ .
  • Fig. 1 also shows the C content of the steel wire for a wire diameter of 1.3 mm ⁇ .
  • a graph comparing the levels of aperture RA with respect to Examples 1 to 9 and Comparative Examples 1 to 3 is shown.
  • the condition where the wire diameter is 1.3 mm ⁇ and the cold working rate is constant is equivalent to the industrial strain of 3.06.
  • a raw screw and a carburized and quenched screw manufactured from a commercially available SWC HI 6A equivalent steel wire manufactured by a conventional technique were set as a comparative example 4.
  • This screw is a M1.6 pan-head screw, and its chemical composition is as shown in Table 27, component No. 9.
  • the manufacturing method is a conventional technique, in which a steel wire is manufactured by hot rolling, and then cold-drawn by a conventional technique to produce a 1.3 mm steel wire, which is then subjected to a spheroidizing annealing treatment.
  • M 1. Pan type machined screws (raw screws) and Ml. 6 pan head screws (carburized and quenched screws) that have been given a predetermined strength by carburizing and tempering the raw screws. It is.
  • a torsion torque test (as described above) was performed using raw screws and carburized and hardened screws as test materials (referred to as “B2 group test materials”). Table 28 shows the test results. Table 28
  • Comparative Example 4 manufactured by a manufacturing method outside the scope of the invention of the present application, the raw screw test material had a low torsional breaking torque of 1.82 kgf As for the case hardened screws, a high torsional strength of 2.96 kgf ⁇ cm is obtained, which is the desired torsional strength.
  • the torsional torque test performed in the above-described example the value was 2.63 kgfcm in Example 6, but in all the tests performed in other examples, it exceeded 2.9 kg kgcm. It has a sufficient torsional strength.

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Abstract

Sont présentés un fil ou une barre d'acier présentant une haute résistance et une excellente usinabilité au froid, ou des articles modelés à haute résistance et un processus de fabrication de ceux-ci. En particulier, il est présenté un processus comprenant le chauffage de 350 à 800 °C d'un lingot d'acier, d'une coulée ou d'un produit d'acier semi-fini ayant un contenu C n'étant pas supérieur à la limite de solution solide du carbone de la phase ferrite au point Ael et pas supérieur à 0,010 % de la masse et être dépourvu de toute cémentite, ou ayant un contenu C >0,01 à 0,45 % de la masse pour obtenir un matériau dont la moyenne du diamètre des grains des cristaux en coupe transversale perpendiculaire à la direction longitudinale soit d’environ 3 mm, et ensuite d'effectuer le travail à froid du matériel pour obtenir la formation d'une structure ferreuse dont la taille moyenne du diamètre des grains des cristaux en coupe transversale perpendiculaire à la direction longitudinale soit d’environ 500 nm.
PCT/JP2005/007352 2004-04-09 2005-04-11 Fil ou barre d’acier présentant une haute résistance et une excellente usinabilité au froid, ou article modelé a haute résistance et processus de fabrication de ceux-ci WO2005106060A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US11/547,972 US20080041503A1 (en) 2004-04-09 2005-04-11 Excellent Cold-Workability Exhibiting High-Strength Steel Wire or Steel Bar or High-Strength Shaped Article, and Process for Producing Them
CN2005800146445A CN1954088B (zh) 2004-04-09 2005-04-11 冷加工性能优异的高强度钢丝、钢棒或高强度成形制品及其制造方法
US12/556,420 US20100051144A1 (en) 2004-04-09 2009-09-09 Excellent cold-workability exhibiting high-strength steel, wire or steel bar or high-strength shaped article, and process for producing them

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2004116168 2004-04-09
JP2004116242 2004-04-09
JP2004-116168 2004-04-09
JP2004-116242 2004-04-09

Related Child Applications (1)

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US12/556,420 Continuation US20100051144A1 (en) 2004-04-09 2009-09-09 Excellent cold-workability exhibiting high-strength steel, wire or steel bar or high-strength shaped article, and process for producing them

Publications (1)

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WO2005106060A1 true WO2005106060A1 (fr) 2005-11-10

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US (2) US20080041503A1 (fr)
CN (1) CN1954088B (fr)
WO (1) WO2005106060A1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BRPI0908575A2 (pt) * 2008-03-04 2015-09-22 Bekaert Sa Nv filamento de aço com baixo teor de carbono trefilado a frio e método de fabricação do referido filamento
WO2010033873A1 (fr) * 2008-09-19 2010-03-25 Fort Wayne Metals Research Products Corporation Fil résistant aux efforts de fatigue, et procédé de production correspondant
CN102019335B (zh) * 2010-11-04 2012-07-04 上海交通大学 调质结构钢的冷锻加工方法
WO2013151009A1 (fr) 2012-04-05 2013-10-10 新日鐵住金株式会社 Tige en fil d'acier ou barre d'acier ayant une excellente forgeabilité à froid
CN102649222B (zh) * 2012-05-31 2014-01-29 浙江振兴石化机械有限公司 一种利用17-4ph不锈钢加工细长轴的方法
KR101655006B1 (ko) * 2012-06-08 2016-09-06 신닛테츠스미킨 카부시키카이샤 강선재 또는 막대강
FR3013736B1 (fr) * 2013-11-22 2016-12-09 Michelin & Cie Procede de trefilage et fil obtenu par ce procede de trefilage
JP6422176B2 (ja) * 2014-08-29 2018-11-14 日産自動車株式会社 高強度ボルト用鋼及び高強度ボルト
CN114985468A (zh) * 2022-06-21 2022-09-02 湖南华菱湘潭钢铁有限公司 一种控制热轧冷镦钢盘卷脱碳层深度的方法

Citations (1)

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JP2004060046A (ja) * 2002-06-05 2004-02-26 National Institute For Materials Science 成形品とその製造方法

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JP2001011575A (ja) * 1999-06-30 2001-01-16 Nippon Steel Corp 冷間加工性に優れた機械構造用棒鋼・鋼線及びその製造方法
KR100464962B1 (ko) * 2001-09-14 2005-01-05 삼화강봉주식회사 냉간압조 특성이 우수한 조질 강선

Patent Citations (1)

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JP2004060046A (ja) * 2002-06-05 2004-02-26 National Institute For Materials Science 成形品とその製造方法

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CN1954088B (zh) 2010-12-08
US20080041503A1 (en) 2008-02-21
US20100051144A1 (en) 2010-03-04
CN1954088A (zh) 2007-04-25

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